The present invention is concerned with vehicle location systems and, more specifically, to vehicle location systems which utilize a radio transmission radiation as the operative means in the location process and is a division of Ser. No. 336,409, filed Feb. 28, 1973.
There is an ever increasing number of vehicles such as police cars, boats and aircraft which are utilizing radio transceivers. Controllers or dispatchers at ground locations, which are in communication with these various vehicles, need to know the coordinate location of the vehicle to carry out their responsibilities such as, for example, coordination of the operation of two or more vehicles, traffic control and rendering aid in distress situations.
In a great number of situations, where the particular vehicle is transmitting, the operator of the vehicle will not know of his exact location or will be unable to relate the location to the ground control station. Accordingly, a vehicle location system is required which can establish the coordinate location of the transmission source based upon the existence of the transmission itself without any location assistance from the particular vehicle operator making the transmission.
Vehicle location systems of the type which determine coordinates of the radiation source from the radiation signal itself have been proposed and built. These systems, however, suffer a common problem of reliability and accuracy in the coordinate determination. One such problem is the drift or variation of various receiving sites due to temperature changes and aging of the components which requires continuous recalibration and updating by ground personnel. A further problem, which is most prominent in ground transmissions, is the effect of multipath or reflected radiation of the signal which produces ambiguous coordinate determinations.